In the digital imaging of x-ray radiation, indirect conversion method that first converts the spatially distributed x-ray energy to light and then capture the light image using two dimensional photo sensors has at least the disadvantage of light scattering before reaching the photo sensors and therefore resulted with the loss of image sharpness. In the case of direct conversion using photo semiconductor material such as amorphous selenium has a significantly higher resolution as a result of no intermediate light conversion and therefore, scattered light does not arise. However, at present, the production of these photoconductive materials is complex and cost-intensive. Furthermore, the x-ray absorption coefficient for this currently commercially successful material, amorphous selenium, is relatively low for x-ray energy above 40 kev. For medical imaging above this energy, thick layer of selenium will be required and again increasing the complexity and cost of production. In recent years, many organic photoconductor (OPC) materials have been developed and successfully utilized in optical copiers and printers. However, since OPC molecules are mostly composed of lower atomic number elements such as carbon, oxygen, nitrogen, hydrogen, and maybe a small percentage of other higher atomic number elements, the x-ray absorption coefficient of these materials are in general, very low and therefore not suitable for x-ray imaging.
An x-ray direct conversion material that has good x-ray absorption coefficient together with the ability of generating electrical charges proportional to the x-ray energy is therefore highly desirable.